diff --git a/Bytes.cpp b/Bytes.cpp
new file mode 100644
index 0000000..b26247f
--- /dev/null
+++ b/Bytes.cpp
@@ -0,0 +1,151 @@
+/***************************************************************************
+ * By Théophile Bastian, 2017
+ * M1 Network course project at ENS Cachan, Juliusz Chroboczek.
+ * License: WTFPL v2 <http://www.wtfpl.net/>
+ **************************************************************************/
+
+/***************************************************************************
+ * Reused from a former project, by Théophile Bastian & Nathanaël Courant
+ * git@github.com:tobast/sysres-pikern.git
+ **************************************************************************/
+
+#include "Bytes.h"
+#include <cstring>
+#include <algorithm>
+using namespace std;
+
+Bytes::Bytes() : data(), firstIndex(0) {}
+
+Bytes::Bytes(const void* buff, size_t len) : data(), firstIndex(0) {
+	data.reserve(len);
+	for(size_t pos=0; pos < len; pos++)
+		data.push_back(((u8*)buff)[pos]);
+}
+
+u8& Bytes::operator[](const size_t pos) {
+	if(pos < size())
+		return data[pos+firstIndex];
+	throw OutOfRange();
+}
+
+u8 Bytes::operator[](const size_t pos) const {
+	if(pos < size())
+		return data[pos+firstIndex];
+	throw OutOfRange();
+}
+u16 Bytes::ushortAt(const size_t pos) const {
+	if(pos+1 < size())
+		return (((u16)data[pos+firstIndex+1])<<8)+data[pos+firstIndex];
+	throw OutOfRange();
+}
+
+size_t Bytes::size() const {
+	return data.size() - firstIndex;
+}
+
+Bytes& Bytes::operator<<(char v) {
+	insertData<char>(v);
+	return *this;
+}
+Bytes& Bytes::operator<<(u8 v) {
+	insertData<u8>(v);
+	return *this;
+}
+Bytes& Bytes::operator<<(u16 v) {
+	insertData<u16>(v);
+	return *this;
+}
+Bytes& Bytes::operator<<(u32 v) {
+	insertData<u32>(v);
+	return *this;
+}
+Bytes& Bytes::operator<<(const Bytes& v) {
+	data.reserve(data.size() + v.size());
+	for(size_t byte=0; byte < v.size(); byte++)
+		data.push_back(v[byte]);
+	return *this;
+}
+Bytes& Bytes::operator<<(const char* str) {
+	unsigned len = strlen(str);
+	data.reserve(data.size() + len);
+	for(unsigned byte=0; byte < len; byte++)
+		data.push_back(str[byte]);
+	return *this;
+}
+
+Bytes& Bytes::operator>>(u8& v) {
+	extractData<u8>(v);
+	return *this;
+}
+Bytes& Bytes::operator>>(u16& v) {
+	extractData<u16>(v);
+	return *this;
+}
+Bytes& Bytes::operator>>(u32& v) {
+	extractData<u32>(v);
+	return *this;
+}
+Bytes& Bytes::operator>>(char& v) {
+	extractData<char>(v);
+	return *this;
+}
+
+void Bytes::operator=(const Bytes& oth) {
+	firstIndex=0;
+	data.clear();
+	data.reserve(oth.size());
+	for(size_t pos=0; pos < oth.size(); pos++)
+		data.push_back(oth[pos]);
+}
+
+Bytes Bytes::sub(size_t beg, size_t len) const {
+	if(beg+len >= size())
+		throw OutOfRange();
+	Bytes out;
+	for(size_t byte=0; byte < len; byte++)
+		out << (*this)[byte+beg];
+	return out;
+}
+
+void Bytes::writeToBuffer(void* buff, unsigned maxLen) const {
+	if(maxLen == 0)
+		maxLen = size();
+	for(size_t pos=0; pos < min((size_t)maxLen, size()); pos++)
+		((u8*)buff)[pos] = (*this)[pos];
+}
+
+char charOfDigit(u8 dig) {
+	if(dig < 10)
+		return dig+'0';
+	return dig+'A'-10;
+}
+void hexdumpByte(Bytes& dest, u8 b) {
+	dest << charOfDigit(b/16) << charOfDigit(b & 0xf);
+}
+
+void Bytes::hexdump(Bytes& dest) const {
+	for(unsigned pos=0; pos < size(); pos++) {
+		hexdumpByte(dest, (*this)[pos]);
+		if(pos % 32 == 31)
+			dest << '\n';
+		else if(pos % 4 == 3)
+			dest << ' ';
+	}
+	if(size() % 32 != 0)
+		dest << '\n';
+}
+
+template<typename T> void Bytes::extractData(T& v) {
+	if(size() < sizeof(v))
+		throw OutOfRange();
+	for(size_t byte=0; byte < sizeof(v); byte++)
+		v = (v<<8) | data[firstIndex+byte];
+	firstIndex += sizeof(v);
+}
+
+template<typename T> void Bytes::insertData(T v) {
+	for(int byte=sizeof(v)-1; byte >= 0; byte--) {
+		data.push_back((u8) (v >> (8*byte)));
+	}
+}
+
diff --git a/Bytes.h b/Bytes.h
new file mode 100644
index 0000000..ca3436f
--- /dev/null
+++ b/Bytes.h
@@ -0,0 +1,79 @@
+/***************************************************************************
+ * By Théophile Bastian, 2017
+ * M1 Network course project at ENS Cachan, Juliusz Chroboczek.
+ * License: WTFPL v2 <http://www.wtfpl.net/>
+ **************************************************************************/
+
+/***************************************************************************
+ * Reused from a former project, by Théophile Bastian & Nathanaël Courant
+ * git@github.com:tobast/sysres-pikern.git
+ **************************************************************************/
+
+#pragma once
+
+#include <cstdlib>
+#include <vector>
+#include <exception>
+
+#include "data.h"
+
+class Bytes {
+	public:
+		class OutOfRange : public std::exception {};
+		/// Exception -- thrown by operator[]
+
+		Bytes();
+		Bytes(const void* buff, size_t len);
+		/// Initializes the object with [buff], reading [len] bytes.
+
+		u8& operator[](const size_t pos);
+		u8 operator[](const size_t pos) const;
+		/// Accesses the [pos]th element. Throws OutOfRange if pos >= size()
+
+		u16 ushortAt(const size_t pos) const;
+		/// Accesses the 16 bits unsigned integet at position [pos].
+		/// Throws OutOfRange if [pos+15] >= size().
+
+		size_t size() const;
+		/// Returns the number of chars in the object.
+
+		Bytes& operator<<(char v);
+		Bytes& operator<<(u8 v);
+		Bytes& operator<<(u16 v);
+		Bytes& operator<<(u32 v);
+		Bytes& operator<<(const Bytes& v);
+		Bytes& operator<<(const char* str);
+		/// Appends the given data to the vector. Returns *this to allow
+		/// chaining.
+
+		Bytes& operator>>(u8& v);
+		Bytes& operator>>(u16& v);
+		Bytes& operator>>(u32& v);
+		Bytes& operator>>(char& c);
+		/// Extracts the given data type from the vector. Returns *this to
+		/// allow chaining.
+
+		void operator=(const Bytes& oth);
+		/// Copies the given Bytes object into its own data.
+
+		Bytes sub(size_t beg, size_t len) const;
+		/// Extracts a sub-bytes, beginning at character [beg], containing
+		/// [len] chars. If [beg+len] >= [size()], throws OutOfRange.
+
+		void writeToBuffer(void* buff, unsigned maxLen=0) const;
+		/// Writes the contents of this array in the buffer [buff].
+		/// The user must provide a buffer of at least [size()] bytes.
+		/// If [maxLen] != 0, writes at most [maxLen] bytes to buff.
+
+		void hexdump(Bytes& dest) const;
+		/// Dumps the packet to [dest] in hexadecimal form.
+
+	private: //meth
+		template<typename T> void insertData(T v);
+		template<typename T> void extractData(T& v);
+
+	private:
+		std::vector<u8> data;
+		size_t firstIndex;
+};
+
diff --git a/main.cpp b/main.cpp
new file mode 100644
index 0000000..be9bae1
--- /dev/null
+++ b/main.cpp
@@ -0,0 +1,13 @@
+/***************************************************************************
+ * By Théophile Bastian, 2017
+ * M1 Network course project at ENS Cachan, Juliusz Chroboczek.
+ * License: WTFPL v2 <http://www.wtfpl.net/>
+ **************************************************************************/
+
+#include "nw_constants.h"
+#include "data.h"
+
+int main(int argc, char** argv) {
+	//TODO read arguments
+}
+